Conversion of hydrocarbon oils



April 19, 1938. J. G. ALTHER CONVERSION OF HYDROGARBON 01L;

Filed June 12, 1935 FRACTIONIATOR e9 a 1 s a1 INVENTOR JOSEPH G. ALTHERFIG.

FURNACE 25 ATTORNEY Patented Apr. 19, 1938 UNITED STATES CONVERSION OFHYDROCARBON OILS Joseph G. Alther, Chicago, Ill., assignor to UniversalOil Products Company, Chicago, 111., a corporation of DelawareApplication June 12,

9 Claims.

This invention refers to an improved. process for the selectiveconversionof relatively lowboiling and high-boiling hydrocarbon oils toproduce high. yields. of desirable light distillate such as motor fuelof good antiknock value.

I! am awarev that many processes have been proposed for the selectiveconversion. of. relatively low-boiling and high-boiling hydrocarbonoils, many of which employ separate heating coils for the differentoils.and which, in many cases, employ a reaction chamber to which the heatedproducts from both. heating coils are supplied and wherein said heatedproducts are subjected to continued conversion- The object of employ-15. ing separate heating coils for the relatively lowboiling andrelatively high-boiling oil is to permit the use of independentlycontrolled conversion conditions of temperature, pressure and time.

for the different oil components. However, it is common practice in suchselective cracking operations employing a single reaction chamber commonto both heating coils to commingle the two streams of heated productsfrom both heating coils either before or immediately after their invtroduction intothe reaction chamber. This practice may be satisfactoryin case it is desirable to retard conversion of the low-boiling. oils(which.

is usuallyv the highest temperature stream) and to increase conversion.of the high-boiling oils in the reaction chamber. This. in turnnecessitates controlling the conversion conditions in the light oilheating coil so that substantially all of the conversion to which thelight oil is subjected occurs in this zone and. controlling theconversion conditions in the heavy oil heating coil so that a,substantial degree of continued conversion of the heavy oil may occur inthe reaction chamber. Obviously this necessitates careful correlation ofthe conditions in the two heating coils with each other and with theconditions maintained in the reaction chamber.

It is the object of the present invention to prevent comm-ingling of thetwo streams of heated.

introducing each of the streams of heated products into the reactionchamber at a remote point in this zone relative to the point ofintroduction of the other stream.

In the preferred embodiment of the present from the other stream. Thisis accomplished by 1935, Serial No. 26,189

invention the reaction zone to which the two streams of heated productsfrom the light oil and heavy oil heating coils are supplied comprises anelongated vertical reaction chamber. The stream of heated products fromeither the lowv boiling or the high-boiling oil heating coil may besupplied to the upper portion of the reaction chamber, depending uponwhich stream it is desired, to subject to independent continuedconversion in this zone, and the stream of heated products'from theother heating coil may be introduced at any desired lower point in thereaction chamber, the commingled streams being withdrawn from the lowerportion of the chamber. On the other hand, one stream of heated productsmay be introduced into the lower portion. of the chamber, the otherintroduced at any desired higherpoint in this zone and the commingledvaporous components of both streams withdrawn from the upper portion ofthe cham- 20 ber. In accordance with another modification of theinvention the stream of heated products from one heating coil may beintroduced into the upper portion of the chamber, the stream of heatedproducts from the other heating coil in- 25 troduced into the lowerportion of the chamber and the vaporous components of two streamscommingled and withdrawn at the desired intermediate point in this zone.In case the first described method of operation is employed, bothvaporous and liquid conversion products may be withdrawn in commingledstate from the lower portion of the reaction chamber or separationthereof may be accomplished therein and the vaporous and liquid productsseparately withdrawn. In case either of the two last described methodsof operation, is employed, separation of vaporous and liquid conversionproducts may be accomplished in the reaction chamber, the liquidconversion products being withdrawn from the lower' portion of this zoneand the vaporous products being removed, as the case may be, from theupper portion or from an intermediate point in this zone.

In one embodiment, the invention comprises subjecting a stream ofhydrocarbon oil of relatively low-boiling characteristics and a separatestream of hydrocarbon oil of relatively high-boiling characteristicseach to independently controlled conversion conditions of elevatedtemperature, super-atmospheric pressure and conversion time in aseparate heating coil, introducing the stream of heated low-boiling oilinto the upper portion of an enlarged vertical reaction chambermaintained at a substantial superatmospheric pressure, introducing thestream of heated relatively high-boiling oil into the lower portion ofthe same reaction chamber, withdrawing nonvaporous liquid conversionproducts from the lower portion of the reaction chamber, comminglingvaporous components of both streams of heated products at anintermediate point in the reaction chamber and withdrawing thecommingled materials therefrom, subjecting the vaporous conversionproducts to fractionation and condensing and collecting fractionatedvapors of the desired end-boiling point as the final light distillateproduct of the process.

The accompanying diagrammatic drawing illustrates one specific form ofapparatus in which the process of the invention may be accomplished aswell as two alternative arrangements for connecting the reaction chamberwith the rest of the system.

Figure 1 of the drawing is a side elevation of the cracking plant;

Figure 2 illustrates a reaction chamber similar to that shown in Figure1 with a different arrangement of connected lines; and

Figure 3 illustrates another modification of the method of connectingthe reaction chamber to the rest of the system which is also within thescope of the invention.

Referring particularly to Figure l of the drawing, hydrocarbon oilcharging stock for the process is supplied through line I and valve 2 topump 3 by means of which it is fed through line 4 and may be directed,all or in part, through line 5 and valve 6 into fractionator l or it maybe supplied, depending upon its characteristics, through line 3, valve 3and line l3 to light oil heating coil [5 or from line 8 through line l6,valve l1 and line 23 to heavy oil heating coil 24. The other oils whichmay be supplied to the light oil and heavy oil heating coils will belater more fully described.

Heating coil 15 is located within a furnace 25 of any suitable form andthe relatively low-boiling oil supplied to this zone is heated thereinto the desired conversion temperature, preferably at a substantialsuperatmospheric pressure and, in the particular case here illustrated,the resulting products are discharged in a continuous stream fromheating coil 15 through line 26 and valve 2! into the upper portion ofreaction chamber 3|.

Relatively high-boiling hydrocarbon oil is supplied, as will be latermore fully described, to heating coil 24 wherein it is heated by meansof heat supplied from a furnace 28 of any suitable form to the desiredconversion temperature, preferably at a substantial superatmosphericpressure and the heated products are discharged in a continuous streamfrom this zone through line 29 and valve 30 and, in the case hereillustrated, enter the lower portion of reaction chamber 3|.

Chamber 31, in the case here illustrated, is. an elongated, verticalchamber of materially increased cross-sectional area relative to thetubes of heating coils l5 and 24 and this zone is pref erably operatedat a substantial superatmospheric pressure, which may be substantiallythe same or somewhat lower than the pressure employed in the precedingheating coil employing the lowest pressure, in case diiferent pressuresare utilized in the two heating coils. When the two streams of heatedproducts from heating coils i5 and 24 enter the reaction chamber in themanner illustrated in Figure 1, liquid components of the stream ofheated products from the heavy oil heating coil will separate fromvaporous. components of the same stream in the lower portion of thereaction chamber to be withdrawn therefrom, as will be later more fullydescribed, while its vaporous components pass upward through the chamberand commingle at an intermediate point in this zone, with the vaporouscomponents of the stream of heated products from heating coil l5,commingled materials being withdrawn from said intermediate portion ofthe chamber through line 32 to subsequent portions of the crackingsystem, as will be later more fully described. The stream of heatedproducts supplied to the upper portion of chamber 3| may, when desired,be directed against the inner surface of the wallsof the chamber bymeans of a suitable spreader flange or spray arrangement such asindicated, for example, at 33 whereby their liquid components which arethus brought in contact with the walls of the chamber may flow downwardthereover to the lower portion of the chamber to be withdrawn therefromtogether with the liquid components of the stream of heated productssupplied to the lower portion of the chamber. lected in the lowerportion of chamber 3| may be quickly removed from this zone through line34 and valve 35 to cooling and storage or elsewhere, as desired, or theymay be directed, all or in part, through line 36 and valve 31 intovaporizing chamber 38, wherein they are subjected to furthervaporization in order to increase their viscosity and flash point and torecover desirable low-boiling components thereof by vaporization, due tothe substantially reduced pressure maintained in chamber 38 relative tothat employed in the reaction chamber. The vaporous conversion productsseparately withdrawn, as previously indicated, from a suitableintermediate point in chamber 3| through line 32 may be directed, allor'in part, through valve 39 in this line into chamber 38 or they may besupplied, all or in part, through line 40, valve 4| and line 42 tofractionator I.

In case chamber 38 is employed it is, as previously indicated,preferably operated at a substantially reduced pressure relative to thatemployed in the reaction chamber by means of which further vaporizationof the liquid conversion products supplied to this zone is accomplished.Final separation of vaporous and residual liquid conversion products isalso accomplished in chamber 38, the latter being removed from the lowerportion of this zone through line 43 and valve 44 to cooling and storageor elsewhere, as desired, while the vaporous conversion products aredirected from the upper portion of chamber 38 through line 45, valve 46and line 42 to fractionation in fractionator I.

The components. of the vaporous conversion products supplied tofractionator l, as previously described, boiling above the. range of thedesired final light distillate product of the process are condensed inthis zone as reflux condensate. The total reflux condensate may becollected within the lower portion of the fractionator to be removedtherefrom through line H! and valve Hi to pump 20 by means of which itis fed through line 2| and may be directed through valve 22 in this lineand through line l3 to further conversion in heating coil l5 or it maybe directed from line 2| through line 41, valve 48 and line 23 tofurther conversion in heating coil 24. Reflux condensate may, on theother hand, be separated by fractional distillation in fractionator I,when so desired, into selected relatively low-boiling and The liquidconversion products thus colhigh-boiling fractions, in which case onlythe relatively high-boiling fractions are withdrawn, as described, fromthe lower portion of fractionator 7, this material being directed frompump 29 through line 2i, line 41, valve 48 and line 23 to furtherconversion in heating coil 24. When this method of operation is employedthe relatively low-boiling fractions of the reflux condensate arewithdrawn from one or a plurality of suitable intermediate points inthis zone, provision being made in the case here illustrated fordirecting the relatively low-boiling oil through line It and valve I! topump l2 by means of which it is fed through line [3 and valve M toheating coil I5 for further conversion.

When the charging stock for the process comprises an oil of relativelywide boiling range, containing an appreciable quantity of bothrelatively low-boiling and high-boiling fractions, it may be supplied,in the manner previously described, to fractionator l and separated inthis zone, together with the reflux condensate, into selected relativelylow-boiling and high-boiling fractions for selective conversion in therespective heating coils l5 and 2d.

Fractionated vapors of the desired end-boiling point are withdrawn,together with uncondensable gas produced by the process, from the upperportion of fractionator I and are directed through line 49 and valve 50to condensation and cooling in condenser 5!. Tne resulting distillateand gas passes through line 52 and valve 53 to collection and separationin receiver 54. Uncondensable gas may be released from the receiverthrough line 55 and valve 56. Distillate may be withdrawn from receiver54 through line 57 and valve 58 to storage or to any desired furthertreatment. When desired, a regulated portion of the distillate collectedin receiver 5 1 may be recirculated by well known means, notillustrated, to the upper portion of fractionator 1 to serve as acooling and refluxing medium in this zone for assisting fractionation ofthe vapors and to maintain the desired vapor outlet temperature.

Referring now particularly to Figure 2 of the drawing, which illustratesa different method of connecting reaction chamber 3! with the otherportions of the system: The highly heated products from the heavy oilheating coil 24 are directed through line 59 and valve 60 into the upperportion of the chamber and may, when desired, be directed against theinterior surface of the walls of the chamber by means of a suitablespreader flange or spray arrangement indicated as before at 33 wherebythe heavy liquid components are contacted with the walls of the chamberand caused to flow rapidly downward thereover while the vaporouscomponents pass downward through the vapor space in the chamber. Thestream of highly heated products from the light oil heating coil l5 aredirected through line SI and valve 62 into the chamber at a suitableintermediate point which, in the case here illustrated, is near itscentral portion. The vaporous products from the heavy oil heating coilare thereby commingled at a point in the chamber adjacent line 6| withthe highly heated products from the light oil heating coil l5 and thecommingled materials pass downward through the remaining or lowerportion of the chamber to be withdrawn, in commingled state and togetherwith the heavy liquids which flow downward over the walls of the chamberand momentarily accumulate in its lower portion, through line 53 andvalve 35%, preferably being introduced therefrom into reduced pressurevaporizing chamber 38. A suitable spreader flange or spray arrangementsuch as indicated at 33 may also be employed, when desired, to directthe liquid components of the stream of heated oil from light oil heatingcoil I5 against the walls of chamber 3 I ,although this provision is notillustrated in Figure 2. Also, when desired, vaporous and liquidconversion products may be separately removed from the reaction chamber,the liquid products being withdrawn therefrom, either alone or togetherwith a regulated portion of the vapors, through line 63 and valve 64,while the total or remaining vaporous products are separately removedfrom a suitable higher point in the chamber through line 13 and valvel4.

Referring now particularly to Figure 3 which illustrates another methodof connecting reaction chamber 3| which is entirely within the scope ofthe present invention, the stream of highly heated products from heavyoil heating coil 24 are directed through line 65 and valve 66 into thelower portion of the reaction chamber wherein their non-vaporous heavyliquid components separate from their vaporous components, the latterpassing upward through the reaction chamber While the liquid productsare withdrawn from the lower portion thereof through line B! and valve68 to chamber 38 or to cooling and storage or elsewhere, as desired. Thestream of heated products from light oil heating coil l5 are introducedinto chamber 3| at a suitable intermediate point through line 69 andvalve ll commingling adjacent their point of introduction with thevaporous components of the heated products supplied to the lower portionof this zone through line 65 and valve 66. A suitable spreader flange orspray arrangement 33 may also be employed, when desired, to direct theliquid components of the products supplied to chamber 3i through line 69and valve 76 against the walls of the chamber so that they will flowdownward thereover and be removed from the lower portion of the chambertogether with the liquid components of the products supplied theretothrough line and valve 66. The commingled vaporous products continue intheir upward path through chamber SI and are withdrawn from the upperportion thereof through line ll and valve #2 to be directed either tochamber 38 or to fractionator l, or in part to both zones in a mannersimilar to that indicated in Figure 1.

It will be understood, of course, that other modified forms of apparatusembodying the features and advantages of the present invention will beapparent to those skilled in the art and the present invention istherefore not limited to the specific forms of apparatus illustrated anddescribed. In each of the three cases illustrated and above describedthe point of introduction of the heated streams of low-boiling andhigh-boiling oils may be reversed. It will also be understood that thevarious modified forms are not to be considered equivalent but ratherserve to render the-process of the invention more flexible and may beselected to suit requirements.

The preferred range of operating conditions which may be employed toaccomplish the objects of the present invention in a process of thegeneral character illustrated and above described may be approximatelyas follows: A temperature of the order of 800 to 950 F. may be employedat the outlet from the heavy oil preferably with a superatmosphericpressure at this point in the system of from to 500 pounds, or more, persquare inch. The temperature employed at the outlet from the light oilheating coil may range, for example, from 900 to 1050 F. and thepressure employed at this point in the system is preferably of the orderof 200 to 800 pounds, or more, per square inch. Any desired substantialsuperatmospheric pressure up to approximately the same as that employedat the outlet from the communicating heating coil employing the lowestpressure may be utilized in the reaction chamber. When a vaporizing orflash distilling chamber is employed it is preferably operated at asubstantially reduced pressure relative to that employed in the reactionchamber ranging, for example, from 100 pounds, or thereabouts, persquare inch down to substantially atmospheric pressure. Thefractionating, condensing and collecting portions of the system mayutilize pressures substantially the same or somewhat lower ran thepressure employed in the preceding stage or" the system.

As a specific example of one of the many possible operations of theinvention as it may be accomplished in an apparatus such as illustratedand above described, charging stock which comprises a Mid-continenttopped crude of about 30 A. P. I. gravity is supplied to thefractionator of the system and there separated, together with the refluxcondensate formed in this zone, into selected relatively low-boiling andhigh-boiling fractions. The low-boiling fractions of the charging stockand reflux condensate, per cent or thereabouts of which boil within therange of approximately 400 to 600 F. are subjected in the light oilheating coil to an outlet coversion temperature of approximately 950 F.at a superatmospheric pressure of about 500 pounds per square inch andthe highly heated products are introduced into the upper portion of thechamber in the manner illustrated in Figure 1 of the drawing. Thehighboiling fractions of the charging stock and reflux condensate aresubjected in the heavy oil heating coil to an outlet conversiontemperature of approximately 920 F. at a superatmospheric pressure ofabout 350 pounds per square inch and the highly heated products fromthis zone are introduced into the lower portion of the reaction chamber.The reaction chamber is maintained at a superatmospheric pressure ofapproximately 350 pounds per square inch. The non-vaporous liquidconversion products which momentarily collect within the lower porton ofthe reaction chamber are quickly removed therefrom and introduced into areduced pressure vaporizing chamber operated at approximately 50 poundsper square inch superatmospheric pressure. Vaporous conversion productsfrom the light oil and heavy oil heating coils are commingled near thecentral portion of the reaction chamber, withdrawn therefrom and alsointroduced into the reduced pressure vaporizing chamber. Residual liquidremaining unvaporized in the vaporizing chamber is withdrawn therefromto cooling and storage as the final residual liquid product of theprocess. The vaporous products from the vaporizing chamber are subjectedto fractionation for the formation of said reflux condensate and thefractionated vapors have an end boiling point of approximately 400 F.are subjected to condensation and the resulting distillate recovered.This operation will produce, per barrel of charging stock, about 62 percent of motor fuel having an octane number of approximately '70 andapproximately 26 per cent of good quality residual liquid suitable forsale as premium fuel oil, the remainder being chargeable, principally,to uncondensable gas.

I claim as my invention:

1. In a process for the pyrolytic conversion of hydrocarbon oils whereinrelatively low-boiling and high-boiling hydrocarbon oils are eachsubjected to independently controlled conversion conditions of crackingtemperature, superatmospheric pressure and conversion time'while passingin a restricted stream through a heating coil, the low-boiling oil beingheated to higher cracking temperature than the high-boiling oil, theseparate streams or heated relatively low-boiling and high-boiling oilsintroduced into an enlarged vertical reaction chamber also maintained atsubstantial superatmospheric pressure, resulting vaporous conversionproducts separated from liquid conversion products in the reactionchamber and the former subjected to fractionation for the recovery ofdesirable light distillate bycondensation of the fractionated vapors,the improvement which comprises introducing the stream of heatedrelatively low-boiling oil into said reaction chamber at a point asubstantial distance remote from the point of introduction thereto ofthe stream of heated high-boiling oil, removing the separated vaporousconversion products from the chamber at a point intermediate the pointsof introduction of said streams thereto, and separately removing theliquid conversion products from the lower portion of the chamber.

2. In a process for the pyrolytic conversion of hydrocarbon oils whereinrelatively low-boiling and high-boiling hydrocarbon oils are eachsubjected to independently controlled conversion conditions of crackingtemperature, superatmospheric pressure and conversion time while passingin a restricted stream through a heating coil, the low-boiling oil beingheated to higher cracking temperature than the high-boiling oil, theseparate streams of heated relatively low-boiling and high-boiling oilsintroduced into an enlarged vertical reaction chamber also maintained atsubstantial superatmospheric pressure and wherein substantial furtherconversion is effected, the resulting vaporous and liquid conversionproducts separated and the former subjected to fractionation for therecovery of desirable light distillate by condensation of thefractionated vapors, the improvement which comprises introducing theheated stream of relatively low-boiling oil into the upper portion ofthe reaction chamber, introducing the stream of relatively high-boilingoil into the lower portion of the reaction chamber, withdrawing liquidconversion products from the lower portion of the reaction chamber andseparately removing vaporous components of both streams from a point inthe reaction chamber intermediate the points of introduction of saidlow-boiling and high-boiling oils.

3. In a process for the pyrolytic conversion of hydrocarbon oils whereinrelatively low-boiling and high-boiling hydrocarbon oils are eachsubjected to independently controlled conversion conditions of cracln'ngtemperature, superatmospheric pressure and conversion time while passingin a restricted stream through a heating coil, the low-boiling oil beingheated to higher cracking temperature than the high-boiling oil, theseparate streams of heated relatively low-boiling and high-boiling oilsintroduced into an enlarged vertical reaction chamber also maintained atsubstantial superatmospheric pressure and wherein substantial furtherconversion is effected, the resulting vaporous and liquid conversionprod- 'llCfiS separated and the former subjected to fracstream-through aheating coil, simultaneously tionation for the recovery of desirablelight distill'ateby. condensation of the fractionated vapors, theimprovement which comprises introducing the stream of heatedrelativelylow-boiling oil into the upper portion of the reactionchamber, causing the liquid components thereof, to flow downward overthe interior surfacev of the walls of the chamber to its lower portion,causing the vaporous components .thereof to pass separately downward inthe reaction chamber, introducing the heated stream of relativelyhigh-boiling oil into the lower portion of the reaction chamber,separating vaporous and liquid components thereof in this zone, causingthe vaporous components thereof to pass upward in the reaction chamber,commingling the vaporous components of both streams intermediate theirpoints of introduction into the reaction chamber, removing thecommingled vaporous products from the chamber and separately removingliquid components of both of said streams from the lower portion of thereaction chamber.

4. In a process for the pyrolytic conversion of hydrocarbon oils whereinrelatively low-boiling and high-boiling hydrocarbon oils are each subjected to independently controlled conversion conditions of crackingtemperature, superatmospheric pressure and conversion time while passingin a restricted stream through a heating coil, the lowboiling oil beingheated to higher cracking temperature than the high-boiling oil, theseparate streams of heated relatively low-boiling and highboiling oilsintroduced into an enlarged vertical reaction chamber also maintained atsubstantial superatmospheric pressure, the resulting vapor- V ous andliquid conversion products separated and the former subjected tofractionation for the recovery of desirable light distillate bycondensation of the fractionated vapors, the improvement which comprisesintroducing the heated stream of relatively high-boiling oil into theupper portion of the reaction chamber, introducing the stream ofrelatively low-boiling oil into the lower portion of the reactionchamber, withdrawing liquid conversion products from the lower portionof the reaction chamber and separately removing vaporous components ofboth streams from a point in the reaction chamber intermediate thepoints of introduction of said low-boiling and high-boiling oils.

5. A process for the conversion of relatively heavy and lighthydrocarbon oils which comprises heating the heavier oil to crackingtemperature under pressure while flowing in a restricted stream througha heating coil, simultaneously heating a stream of the lighter oil tohigher cracking temperature under pressure in a second heating coil,introducing the heated oil streams into an enlarged vertical reactionchamber maintained under superatmospheric pressure, the heated light oilstream being introduced to the chamber at a point a substantial distanceremote from the point of introduction of the heated heavy oil stream,separating vaporous from liquid conversion products in the chamber,removing the separated vaporous products from the chamber at a pointintermediate the points of introduction of said streams thereto andseparately removing the liquid conversion products from the lowerportion of the chamber.

6. A process for the conversion of relatively heavy and lighthydrocarbon oils which comprises heating the heavier oil to crackingtemperature under pressure While flowing in a restricted heating astream of the lighter oil to higher cracking, temperature under pressurein a second heating coil, introducing the heated light oil the chamber,separating vaporous from liquid jCOllVBISiGII products in the chamber,removing the separated vaporous products from the chamber at a pointintermediate the points of introduction of said streams thereto, andseparately removing the liquid conversion products from the lowerportion of the chamber.

'7. The process as defined in claim 6 further characterized in that theheated heavy oil stream is introduced to the upper portion of thechamber while the heated light oil stream is introduced at asubstantially lower point in the chamber.

8. In a process for the pyrolytic conversion of hydrocarbon oils whereinrelatively low-boiling and high-boiling hydrocarbon oils are eachsubjected to independently controlled conversion conditions of crackingtemperature, superatmospheric pressure and conversion time while passingin a restricted stream through a heating coil, the low-boiling oil beingheated to higher cracking temperature than the high-boiling oil, theseparate streams of heated relatively low-boiling and high-boiling oilsintroduced into an enlarged vertical reaction chamber also maintained atsubstantial superatmospheric pressure and wherein substantial furtherconversion is effected, the resulting vaporous and liquid conversionproducts separated and the former subjected to fractionation for therecovery of desirable light distillate by condensation of thefractionated va-- pors, the improvement which comprises introducing theheated stream of relatively low-boiling oil into the upper portion ofthe reaction chamber and passing the liquid and vaporous componentsthereof downward in the chamber, introducing the heated stream ofrelatively high-boiling oil into the lower portion of the reactionchamber, separating vaporous and liquid components thereof in this zone,causing the vaporous components thereof to pass upward in the reactionchamber, commingling the vaporous components of both streamsintermediate their points of introduction into the reaction chamber,removing the commingled vaporous products from the chamber intermediatethe points of introduction of the heated streams to the chamber, andseparately removing liquid components of both of said streams from thelower portion of the reaction chamber.

9. In a process for the pyrolytic conversion of hydrocarbon oils whereinrelatively low-boiling and high-boiling hydrocarbon oils are eachsubjected to independently controlled conversion conditions of crackingtemperature, superatmospheric pressure and conversion time while passingin a restricted stream through a heating coil, the low-boiling oil beingheated to higher cracking temperature than the high-boiling oil, theseparate streams of heated relatively low-boiling and high-boiling oilsintroduced into an enlarged vertical reaction chamber also maintained atsubstantial superatmospheric pressure and wherein substantially furtherconversion is effected, the resulting vaporous and liquid conversionproducts separated and the former subjected to fractionation for therecovery of desirable light distillate by condensation of thefractionated vapors, the improvement which comprises introducing one ofthe heated streams into the upper portion of the reaction chamber andpassing the liquid and vaporous components thereof downward in thechamber, introducing the other heated oil stream into the lower portionof the reaction chamber, separating vaporous and liquid componentsthereof in this zone, causing the vaporous com- 10 ponents thereof topass upward in the reaction

